Enterohemorrhagic Escherichia coli (EHEC)

characteristics of Escherichia coli

- gram-negative bacteria

- rod-shaped

- facultative anaerobe (can grow using oxygen or without oxygen)

- has peritrichous flagella (over the whole surface)

What is the background of the strain Escherichia coli O157:H7?

It is an emerging cause of foodborne illness, initially isolated in Argentina in 1977, and associated with severe bloody diarrhea.

What is E. coli O157:H7 often referred to as?

Hamburger disease, due to outbreaks in 1982, was linked to contaminated hamburgers that caused severe bloody diarrhea

Where do most strains of E. coli live?

Most live in the intestines of healthy humans and animals, part of the normal flora, and are harmless

How many cases and deaths of STEC infection occur annually in the United States?

Estimated 265,000 cases with 61 deaths.

What was a notable outbreak of E. coli O157:H7 in the United States?

An outbreak at Golden Corral in Kearney, NE, in February 1999, with 72 cases and 8 hospitalizations due to contaminated iceberg lettuce.

What does the 'O' and 'H' in E. coli O157:H7 refer to?

'O' refers to the lipopolysaccharide antigen and 'H' refers to the flagellar antigen.

What toxin does E. coli O157:H7 produce and what is its effect?

It produces a shiga-like toxin that destroys cells lining the large intestine and can lead to bloody diarrhea. When it enters the bloodstream stream it kills erythrocytes (red blood cells) and endothelial cells that line blood vessels

What makes E. coli O157:H7 so dangerous?

It can survive the acidic conditions of the stomach, and antibiotics will lead to the release of the Shiga toxin

How does the Shiga toxin affect host cells?

It stops host cell protein synthesis by cleaving 60S ribosomal RNA, preventing protein elongation. This leads to mucosal damage and bloody diarrhea.

What are the primary symptoms of E. coli O157:H7 infection?

Abdominal cramps, diarrhea that progresses to bloody diarrhea, possible fever, and vomiting

What severe condition can develop from an E. coli O157:H7 infection?

Haemolytic uraemic syndrome (HUS), which can lead to kidney failure.

Who is most susceptible to developing Haemolytic uraemic syndrome (HUS) from E. coli O157:H7 infection?

Children under 5 years of age and the elderly.

How is E. coli O157:H7 diagnosed?

Isolation in stool samples using Sorbitol MacConkey (SMAC) agar.

What is the role of Sorbitol MacConkey (SMAC) agar in diagnosis?

It selectively inhibits Gram-positive flora and differentiates E. coli O157:H7, which cannot utilize sorbitol on a plate, so it does not turn red in comparison to other E. coli strains

What are common sources of E. coli O157:H7 contamination?

Ground beef, unpasteurized apple cider, yogurt, cheese, unpasteurized milk, fruits, vegetables, and sewage-contaminated water, and petting zoos

What preventive measures can be taken against E. coli O157:H7?

Cook meat (COOK THAT PATTY BABY) thoroughly to 72˚C (160˚F), avoid undercooked meat, drink pasteurized products, and wash fruits and vegetables.

What is the main reservoir for E. coli O157:H7?

Cattle, with 50% of feedlot cattle carrying the organism.

What is the effect of the shiga toxin on erythrocytes?

It can kill erythrocytes (red blood cells) and damage endothelial cells in blood vessels.

What is the typical duration for recovery from an E. coli O157:H7 infection?

Illness typically resolves in 5 to 10 days.

Why should E. coli O157:H7 infections not be treated with antibiotics?

Antibiotics can worsen the condition and increase the risk of HUS, as it will trigger the release of Shiga toxin

How many organisms are needed to cause disease from E. coli O157:H7?

Only about 100 organisms are needed to cause disease.

What is the significance of horizontal gene transfer in E. coli O157:H7?

It acquired the gene encoding Shiga toxin through horizontal gene transfer.